Abstract

Amplitude versus offset (AVO) curves are extracted from 2.5-D
finite-difference simulations of ground-penetrating radar (GPR)
reflection responses, of a layered model, to horizontal
transverse-electric dipole excitation at the air-earth interface.  The
model parameterization is in terms of Cole-Cole relaxation mechanisms.
This allows explicit separation of the effects, of conductivity and
the frequency-dependent components of the complex dielectric
permittivity and of the complex magnetic permeability, in reflection
responses as a function of antenna separation. The amplitude and phase
effects of antenna directivity are automatically incorporated into the
simulated responses. Reflections associated with contrasts in
dielectric and magnetic relaxations are much smaller than those
associated with contrasts in permittivity, conductivity, and
permeability. For typical earth materials, attenuation of propagating
GPR waves is most strongly influenced by conductivity, followed by
dielectric relaxation, followed by magnetic relaxation.  Reflection
magnitudes and AVO curve shapes are very different depending on the
contrast in electromagnetic properties that caused the reflection.
Thus, the potential is shown for extraction of detailed
electromagnetic properties from GPR AVO observations.

It is necessary to use frequency-dependent simulations/predictions in
analysis of field GPR data when amplitude information is to be
interpreted in terms of the distribution of electromagnetic properties.